1. Field of the Invention
The invention generally relates to brakes. More specifically, the invention relates to rod or wheel brake, especially to an intermittent brake. A positive lock brake is applied to a rotating rod, such as to an automotive steering wheel shaft. The mechanism permits the shaft to rotate through a limited, preselected arc. At the end of the preselected arc, the mechanism applies a positive lock in the direction of rotation. A mechanism of this type is useful in conducting dynamic testing of vehicle performance.
2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98
Evaluating the performance characteristics of a car, truck, other land vehicle, or water vehicle can require performing repeated dynamic evaluations. Often such testing requires that an expert test driver perform a defined maneuver, and such a maneuver may be repeated a plurality of times under similar or controlled conditions. In order to aid the test driver in accurately repeating a test, it is desirable to limit certain aspects of vehicle performance. These limitations may include, for example, speed and available degree of steering wheel rotation. Every vehicle has inherent maximum limits for these factors; but for testing purposes, it is desirable to apply limits other than inherent maximums. As one example, for accident reconstruction it may be desirable to drive the vehicle under conditions similar to those present at the time of the accident.
One desirable limitation in such evaluations is the permitted arc of rotation for the steering wheel. Only in the unusual case is maximum available arc of steering rotation to be used in an evaluation. Typically, a test will require a preselected arc of steering wheel rotation less than the maximum. This arc often is less than two turns from neutral wheel position. Because the arc may be more than one full revolution, a simple abutment stop cannot be used in every situation.
Computerized steering systems can control and repeat any specified pattern of steering wheel rotation. Such systems cannot be used in every case. A computerized system often is designed for use with only a specific vehicle or type of vehicle. When evaluating a specific vehicle that has been involved in an accident, it may be impractical or impossible to find and install a computerized system suitable for use with the selected vehicle. Further, computerized steering systems tend to be technically complex and correspondingly costly, which serves as a practical prohibition against using them in many testing situations.
It would be desirable to have a widely adaptable steering limiter that can be simply and readily installed on a test vehicle. Further, it would be desirable to have a steering limiter of this type that is adjustable to permit a variably selectable angle of maximum steering wheel rotation.
Various devices appear in United States patents for limiting rotation of a wheel or shaft.
U.S. Pat. No. 4,751,986 to Takahashi shows a rotor that is provided with a stop. An arcuate stator is spaced from the rotor and carries two stops, spaced apart by a specified angle. A ball circulates in the gap between the rotor and stator and between the two stops of the stator. The rotor can rotate in either direction. The rotor stops when the stop on the rotor has pushed the ball against either of the stops on the stator. From one extreme to another, the rotor can rotate between one and two rotations. This system could offer an ability to control available rotation either by starting the ball in a predefined starting position between the stops or by adjusting a spacing between the two stops on the stator. However, this system is not readily adapted to be installed on any selected vehicle. Further, adjustment requires considerable pre-fabrication and complexity.
U.S. Pat. No. 4,191,301 to Hickman et al. shows a rotating main shaft that carries an extending lug. On each revolution, the lug strikes a boss on a neighboring counting wheel, advancing the wheel by a partial turn. One of the bosses on the counting wheel eventually will reach and contact a fixed stop lug that prevents further turning of the counting wheel. This stop event also prevents further rotation of the main shaft in the initial direction. The number of bosses on the counting wheel determines how many times the shaft can rotate in one direction before the stop event. As taught in the patent, this system offers no fine adjustment of less than one turn of the main shaft. A possible, but untaught, modification to increase fine adjustment is to provide multiple extending lugs on the shaft to reach the stop point after one or more partial turns. However, this type of adjustability requires specific pre-fabrication to conform to each different degree of desired steering wheel rotation. Thus, this system is not well suited for variable testing.
U.S. Pat. No. 2,746,573 to Hastings shows a two-sided system for allowing more than one turn between the two sides of the system. One side of the system is a spiral spring that provides a spiral groove pathway between the spring walls. The second side of the system provides a follower block that is slidable on a radial pathway. As the two sides relatively rotate, the follower block moves radially in the spring grooves until it reaches a stop at either end of the pathway. It is not evident how this system could be applied to a pre-installed steering shaft and variably adjusted for a selected degree of wheel angle.
U.S. Pat. No. 2,744,416 to Feigin shows a system of fixed stops on two meshing gears with different numbers of teeth. Due to differential gear ratios, after a determinable number of rotations, the fixed stop on each gear meets the fixed stop on the other. This technique can be used to predetermine almost any number of rotations. However, this system is not well suited for use on a pre-installed steering shaft. It would present problems in installing a gear over the shaft, and it would require suitable differential gears for each different selected steering angle. These limitations cause this system to be poorly suited for use on different vehicles and for variable steering angles. U.S. Pat. No. 5,239,490 to Masaki et al. shows a computerized electronic apparatus for precisely detecting the rotation of a steering wheel and steering shaft. The apparatus employs a microprocessor to analyze the detected signals and operate an electronic power steering system or other rotating device. This system is applied for the purpose of controlling rotation in response to inputs, rather than to limit rotation. Nevertheless, changing this mode of operation may be possible. This patent is an example of a computerized steering system, mentioned above. The chief important limitations are high cost, difficult or impossible adaptability to different vehicles, and lack of suitability for use when a test driver is controlling the vehicle.
U.S. Pat. No. 3,055,235 to Turley shows a planetary gear system that provides indexing motion through a specified arc. This patent shows general background. As evident from the scope of the prior art, suitable devices of the desired kind are unknown. While several mechanisms perform a related function, they are not sufficiently versatile in their applications and structures to be adapted for mounting on the steering system of substantially any test vehicle. As a result, the need to provide a positive and variable rotation lock for dynamically testing substantially any selected vehicle is not reasonably met.
To achieve the foregoing and other objects and in accordance with the purpose of the present invention, as embodied and broadly described herein, the method and apparatus of this invention may comprise the following.